How to remove underscore between two numbers in all files in a directory

Question

So I have a directory with nested folders, and at some point there are .png images.

The naming of these images is like this "letters_numbers_numbers_letters.png", and I want to delete the underscore between the numbers.

Say that we have a file named a_1_2_b.png, I want to rename it to a_12_b.png. I know I have to use something like:

find . -name "*[0-9]_[0-9]* -type f -exec bash -c <enter_code here>`

but I'm not sure how to specify how to delete this specific underscore. Remember there are two other underscores I don't want to touch.

Thanks in advance!

Answer 1

Use one of the variants of perl's rename. For instance, with that one (rename package in Debian-like systems):

LC_ALL=C find . -name '*[0-9]_[0-9]*' -type f -exec rename -n -d '
  s/(?<=\d)_(?=\d)//g' {} +

(remove the -n (dry-run) when happy).

With zsh, you could do:

autoload -Uz # best in ~/.zshrc
zmv -n  '(**/)(*[0-9]_[0-9]*)(#qD.)' \
        '$1${2//(#m)[0-9][_0-9]#[0-9]/${MATCH//_}}'

It's a bit more complicated, as there's no equivalent of perl's look-around regexp operators in zsh globs.

Those remove all the _s that are surrounded by digits in every regular file's name (would rename the dir_1_2_3/file_1_2_foo_22_3_4_bar file to dir_1_2_3/file_12_foo_2234_bar for instance).

To only remove the second _ in regular files that follow the letters_digits_digits_letters.png pattern, that would just be:

zmv -n '(**/)([[:alpha:]]##_<->)_(<->_[[:alpha:]]##.png)(#qD.)' \
       '$1$2$3'